Voltage Tester for $7(expired)
Non-contact voltage tester for $11, and click the $3 coupon under the price.
If you feel like attempting electrical work yourself, this tool can be very helpful.
For example, if you bought "smart" light switches, replacing existing switches will involve handling electrical wires.
Figuring out which wire is "hot" is important, because touching a "hot" wire will result in electrocution.
Even with the power shut-off, it's best to be very sure by getting a second opinion with a tester like this.